Apparatus for muffling noise and engine exhaust gases



May 4, 1965 E. H. SCHOMBURG 3,181,647 APPARATUS FOR MUFFLING NOISE AND ENGINE EXHAUST GASES Filed Oct. 18, 1963 2 Sheets-Sheet 1 INVENTOR. f'awaru H .Sc/zamag BY 9 4, w 1 Q fitter/w gs,

May 4, 1965 E. H. SCHOMBURG APPARATUS FOR MUFFLING NOISE AND ENGINE EXHAUST GASES Filed Oct. 18, 1963 2 Sheets-Sheet 2 INVENTOR. Edward )1 $a/zamur BY M1141 w? M qzi'ziawnegs.

United States Patent 3,181,647 APPARATUS FOR MUFFLING NOISE AND ENGINE EXHAUST GASES Edward H. Schombnrg, Rte. 2, Warren, Ind. Filed Oct. 18, 1963, Ser. No. 317,186 6 Claims. (Cl. 181-54) The present invention relates to an apparatus and method of muflling noise and more particularly to muffling noises in the exhaust gases of internal combustion, reciprocating, piston-type engines. I

Mufflers used in conjunction with internal combustion, reciprocating piston-type engines are conventionally connected to the exhaust pipe circuit of the engine so that the exhaust gases must pass therethrough before being exhausted into the atmosphere. Several varieties and designs of mufiiers have been proposed, all of which operate on the same physical principles. It is generally known that sound waves traveling through air have appreciably straight paths, absent any interference from other objects. Only by reflecting from relatively solid objects do sound Waves travel around corners. It is also readily known that sound waves are continuously being reduced in loudness by the cushioning effect of the supporting gas medium either upon a reflection or change in direction, an encounter with air turbulence, or an impingement upon a relatively stagnant gas. Energy is thus lost from the sound wave, resulting in a muffling of the sound. While numerous mufflers have been proposed, all of the designs have a series of restricted passages through which the exhaust gases must pass. These restrictions set up various amounts of turbulence and tagnant air pockets. Mufflers that have been proposed utilize various and sundry structures for this purpose and result in various degrees of success in mufliing engine noises.

Prior muiflers have been generally of two types: singlepass mufflers and multi-pass mufflers. Of these types, the multi-pass muflier has greater capabilities of Inufiiing noises in exhaust gases due to the several changes of direction in gas flow within such mufflers and therefore are highly desirable. However, every change of direction of gas flow or restriction of gas flow results in a requisite pressure drop. This places a limitation on the number of restrictions or flow reversions possible in any given muffier as the exhaust gases of the engine must be permitted to flow out of the engine cylinder for preferred engine operation. Whenever the flow restriction becomes appreciable across any muflier system, a portion of the exhaust gases are left in the engine cylinder thereby occupying space that could be occupied by a combustible air-gasoline mixture. This results in a direct loss of power and a less efficient engine operation. It is therefore desirable to provide a simple, inexpensive and efficient multipass mufller for internal combustion engines, having a relatively unrestricted gas flow therethrough. While various multi-pass mutfier systems have been proposed, those having relatively unrestricted gas flow have not had sufficient mufliing properties, while those having suificient mufliing properties have generally caused losses in engine performance and economy. It is therefore desirable to provide a new and novel method of muifling exhaust gases from internal combustion engines that can be incorporated into a muffler having the aforementioned desired qualities.

It is therefore an object of this invention to provide a unique method of rnuifling exhaust gases from internal combustion engines that is easily and inexpensivelyemployed in a muffler structure that has eflicient muifling properties and does not appreciably restrict gas flow therethrough. V

It is another object of this invention to provide an improved muffier utilizing the unique method of this invention.

It is still another object of thisinvention to provide an improved multi-pass muflier system wherethrough gas flow is relatively unrestricted.

It is still another object of this invention to provide a simple, efiicient and inexpensive multi-pass mufiier structure.

Further objects and advantages of my invention will become apparent by reference to the following description and the accompanying drawings and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

The invention in its broader aspects provides a method of silencing noises in flowing gas streams comprising the steps of selectively varying the gas velocity, beneficially introducing turbulence into the flowing gases, and reversing the direction of the flow of gases at various times before the flow of gases are exhausted to the atmosphere.

The invention in its broader aspects also provides an engine muffler comprising a first chamber, a tube leading to the second chamber, a plurality of third chambers mounted by perforated baffles, a fourth chamber, a tube leading from the fourth chamber to the fifth chamber, and an exit leading therefrom to the atmosphere.

In the drawings, each figure is drawn to scale:

FIG. 1 is a side view, in cross-section of a three-pass mufiier, an apparatus that utilizes the unique method of this invention;

FIG. 2 is a perspective view of the perforated tubes incorporated in the muffler of FIG. 1

FIG. 3 is a cross-sectional fragmentary view taken along the line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along the line 4-4 of FIG. 1; and

FIG. 5 is a cross-sectional view taken along the line 55 of FIG. 1.

Referring to the drawings, there is shown at 10 a metallic mufiier barrel that is closed at both ends by closure plates 12 having central openings 14 through which exhaust gases enter and exit from the muffler. Fixedly positioned within barrel 10 are two metal tubes 16 substantially equal in length and identical in all respects, which are fixedly attached to each other at their surfaces in a manner that their axes are parallel and define a single plane. Tubes 16 are not coterminous, each tube is longitudinally offset to the other having approximately onethird of its length overhanging one end of the other tube. Mounted in this fashion, tubes 16 are fixedly attached within barrel 10 essentially equally distant from end plates 12 and centrally located in the circular cross-section of the barrel 10 by means of baffle plates 20 and 22 which are secured to tubes 16 and the inner surface 24 of barrel 10.

Tubes 16 are slightly deformed from a generally cylindrical shape by means of a longitudinal indentation 28 in the tubes surface. As more clearly shown in FIGS. 2, 4 and 5, the crossection of tube 16 is circular except for the indentation 28. Indentation 28 is formed during the process of cutting pressure relief holes 26 which are aligned with and located at the bottom of longitudinal indentation 28 in tubes 16. A line drawn through the centers of pressure relief holes 26 on the surface of each of tubes 16 is parallel and in a plane with the axis of the tube 16 as they are mounted in barrel 10. Pressure relief holes 26 are formed in tube 16 by cutting two relatively short longitudinal and parallel slits in tube 16 aligned with the axes thereof, and connecting the ends of the two slits by a third slit, thereby forming a rectangular tab 30. Tab 39 is then pressed into said tube forming a pressure relief hole 26 and at the same timetab 30 is formed and positioned so as to protrude from the interior surface 32 of tube 16. In production, pressure relief holes 26 are made in a single press-stamping operation that slits tube 16 and depresses tab 36 into tube 16 all in a single operation. Because of the force applied to tube 16 during this press stamping operation, longitudinal indentation 28 is formed. Also because of the method of forming pressure relief holes 26, the hole edge perpendicular to the tube axes has at the interior surface 32 a knife edge 34. FIG..1, tubes 16 are fastened together in such amanner that tabs 31) slope in the direction of gas fiow and knife edges 34 face in the opposite direction. However, for other applications, tabs 30 and knife edges 34 may be positioned in opposite directions.

Baffie plates 20, more clearly shown in FIG. 5, are disc-shaped, having a perpendicular, annular flange 36 and a single opening 38 therein. Opening 38 is circular, having a diameter approximately equal to the outside diameter of tube 16 and having as one point on its circumference the center of the disc-shaped bathe plate 20. In assembling the. mufller of FIG. 1, a single tube 16 is inserted into hole 38 such that longitudinal indentation 28 is most adjacent interior surface 24 of barrel 10.

Baffle 20 is secured to tube 16 adjacent an end by welding at 40 and secured to interior surface 24 of barrel 1t) solely by means'of a frictional fit between flange 36 and surface 24.

Baffles 22, more clearly shown in FIG. 4, are discshaped and have a perpendicular annular flange 42. Baffles 22 have three circular openings 44 which overlap and form a single opening therein, each circular opening 44 having a diameter approximating the diameter of tubes 16 and each having its center located on the same diameter of baffle '22. One of the three openings 44 has as its center the center of baffle 22, the other openings 44 have the center of bafile 22' as a point on the circumference, thereby providing for an ample overlap of the three circular openings. In assembling the muffler of PEG. 1, tubes 16 are inserted into the two outermost openings 44 with their pressure relief openings 26 most adjacent the inner surface 240i barrel 10. Tubes 16 are then welded together at 46 and secured to baffle plate 22 by welding at 48. Approximately one-third of the central opening 44 is left unobstructed, thereby forming openings 51) on either side of tubes 16. Baffle plates 22 are secured to barrel 10 solely by means of a' frictional fit between annular flange 42 and interior surface 24.

As assembled, the three-pass muflier shown in FIG. 1 is divided'into five compartments, indicated by A, B, C, D, B, respectively. Compartments A and E are relatively sealed except for the relatively small opening 56 between the longitudinalindentation 28 and baffles lit and 22 (see FIG. compartments B, C and D are relatively loosely sealed, having interconnecting open- I ings 5% in baffie plates 22. Compartments A and D and compartments B and E are directly interconnected by means of tubes 16; compartments B, C and C, D are directly interconnected by openings 50. The other combinations of the compartments as above-mentioned, i.e., A and B, A and C Aand E, B and D, C and E, C and D, and D and E, are connected only by means including theopenings 26 in the tubes 16' and spaced from each other. In actuality, however, pressure relief holes 26 allow gases passing from chamber A to D and chamber B to E, through tube 16,,to leak into chambers B and C andchambers C and D, respectively.

The three-pass muifler' illustrated in FIG. 1 utilizes th method of this invention of silencing noises. Therefore, the detailed description of the operation of the mufller of FIG. 1 will also describe the method of my invention. As is evident from the physical laws governing gas flow, turbulence is interjected into the flowing gas stream at several points within the muffler structure shown in FIG.

In the muffler shown in 1. To enumerate only the more obvious turbulenceforming structures, attention should be directed to each of the exits 58 of relatively small tubes into relatively large chambers and the reversal of gas flow after each exit 58, each of the entrances 6d of relatively small, tubes from relatively large chambers, the tabs 30 protruding from the interior surface 32 of tube 16, and the orifice type structures of openings 50in baffle plates 22.

As is further evident from the physicallaws governing gas flow, the gas flows between tubes 16 and chambers A, B, C, D andE and between adjacent chambers are solely controlled by the relative dimensioning of the respective openings therebetween. As described herein, the magnitude of each gas flow and their relative size to each other provide the improved mutfling characteristics of the specific embodiment shown in the scale drawings of FIGS. 1 to 5. In that specific embodiment, barrel 10 has a diameter of four (4) inches. Tubes 16 have a diameter of onev and three-quarters (1%) inches and a single row of pressure relief holes 26 extending axially, the holes 26 being on one-half inch centers and one-quarter /4) inch square.

In operations, engine exhaust gases enter through hole 14 in closure plate 12 into chamber A in the direction 7 shown by arrow 51. The gases collected in chamber A are then removed from chamber A by means of tube 16,

having tabs 30 sloped in the direction of flow. indicated by arrow 52. The exhaust gases are increased in velocity upon entrance into tube 16 by means of the relatively small cross-section of tube 16 compared to that of chamber A. Pressure relief openings 26 allow a portion of the exhaust gases flowing through tube '16 to escape into chambers B and C, resulting in a gas pressure within tube 16 lower than that calculable by normal gas flow equations. Gases flowing through tube 16 then exit into chamber D and are impinged against a relatively stagnant gas layer adjacent baffle 20. Upon exit from the tube 16, the gas chamber A. The exhaust gasespass from chamber D through openings 50 in bafile'plates 22 into chamber C, thereby flowing in a direction opposite that shown by arrow 52. The velocity of the gases in chamber D is relatively slower than the velocity of the gases flowing through tube 16, as aforementioned, and likewise the velocity of the gases flowing through openings 50 is relatively faster than either the gas velocity in chamber D or in chamber C. Also, a further drop in pressure is observed as the gases flow through opening 50 from chamber D to chamber C, thereby providing a lower pressure in Chamber C than in chamber D and an appreciably lower pressure inchamber C than in tube 16 flowing into chamber D, thereby providing for a gas'flow from tube 16 to chamber C. Gases from chamber C exit either into chamber B through openings 50 of baffle plates 22' or exit through pressure relief holes 26 into the tube 16 transporting gases from chamber B to chamber E in the direction of arrow 54. The gases flowing into chamber B from chamber C experience a pressure drop and an. increased velocity traveling through the openings 50 similarly to the flow of gases from chamber D into chamber C. Thus the flow of gases through openings 50 in bafiie plates 22 provides a lower gas pressure in chamber B than in chamber D or chamber C. Relatively swift gases emerging from openings 50 into chamber B are impinged against another relatively stagnant gas layer immediately adjacent baffle 20, and thereupon, reversed in the direo tion of flow so as to enter the second-mentioned tube 16, exiting from chamber B and interconnecting chambers B and E. Gases of chamber B upon entering tube 16 are further reduced in pressure. and are again increased in velocity. As gases from chamber C are entering tube 16,

as well as gases from chamber B, morergas arrives at f chamber 9 than enters tube 16 from chamber B. All of the gas entering tube 16 from chamber A eventually arrives in chamber E and collects until exited through opening 14 in closure plate 12.

While there have been described above the principles of this invention in connection with specific'apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.

What is claimed is: r

' I. A three-pass engine muffler comprising an elongated tubular barrel having an axis and opposite first and second ends; first and second elongated tube members havingaxes and being disposed within said barrel, the axes of said barrel and tube members being parallel and lying in a single plane, said tube members being of substantially equal size and being secured together in side-by-side and longtitudinally ofiset relation whereby one end portion of each tube member extends beyond the adjacent end of the other tube member, two closure plates on the opposite ends, respectively, of said barrel, entrance and exhaust tubes secured to said two closure plates, respectively, communicating with the interior of said barrel, a first disc-shaped bafile plate having an axially extending flange on the perimeter thereof, said bafile plate being frictionally fitted into said barrel and being disposed at right angles to the axis of said barrel, said first baffle plate being spaced from one of said closure plates thereby forming a first compartment therewith, said bafile plate having an opening which receives in sealing relation the distal end of the end portion of one tube member thereby establishing communication between said first compartment and said one tube member, a second disc-shaped baffie plate having an axially extending flange on the perimeter thereof, said second bafile plate being frictionally fitted into said barrel and being disposed at right angles to the axis of said barrel, said second baffie plate being spaced from the other of said closure plates thereby forming a second compartment therewith, said second baffle plate having an opening which receives in sealing relation the distal end of the end portion of the other tube member thereby establishing communication between said second compartment and said other tube member, both said tube members having a plurality of longitudinally spaced apertures therein arranged in a straight line located in said plane of said axes adjacent to the periphery of said barrel, said apertures extending from one end to the other of each tube member, a plurality of deflector tabs on said tube members adjacent to said apertures, respectively, and extending inwardly of said tube members,, there being one tab for each aperture, said tabs being secured to said tube members and angling inwardly in a direction extending from said first barrel end toward the second barrel end, and a third disc-shaped baffle plate having an axially extending flange on the perimeter thereof, said third baflle plate being frictionally fitted into said barrel and being disposed at right angles to the axis of said barrel, said third baflle plate being spaced'from and disposed between said first and second bafile plates thereby defining additional compartments, said third bafiie plate having two diametrically spaced openings which receive, respectively, said two tube members, said third bafile plate being secured to said two tube members, and a clearance opening provided in said third bafile plate in the central portion theresof adjacent to said two tube members for providing direct communication between said additional compartments.

2. The muffler of claim 1 including a fourth disc-shaped bafile plate having an axially extending flange on the pe rimeter thereof, said fourth bafile plate being frictionally fitted into said barrel and being disposed at right angles to the axis of said barrel, said fourth plate having three diametrically spaced openings, the outermost of the lastmentioned openings, respectively, receiving said two tube members, said fourth baflle plate being secured to said two tube members, the middle of said three openings forming a clearance between said fourth plate and said tube members for providing direct communication between the compartments on opposite sides of said fourth plate, said third and fourth baifie plates being spaced from each other and from said first and second baflle plates thereby defining three tandemly arranged compartments, the two ends of said two tube members which are set back from said end portions communicating with the two endmost of said three compartments, respectively.

3. A three-pass engine muffler comprising an elongated tubular barrel having an. axis and opposite first and second ends; first and second elongated tube members having axes and being disposed within said barrel, the axes of said barrel and tube members being parallel and lying in a single plane, said tube members being of substantially equal size and being secured together in side-by-side and longitudinally offset relation whereby one end portion of each tube member extends beyond the adjacent end of the other tube member, two closure plates on the opposite ends, respectively, of said barrel, entrance and exhaust tubes secured to said two closure plates, respectively, communicating with the interior of said barrel, a first discshaped baflle plate fitted into said barrel and being disposed at right angles to the axis of said barrel, said first bafile plate being spaced from one of said closure plates thereby forming a first compartment therewith, said baffie plate having an opening which receives in sealing relation to distal end of the end portion of one tube member thereby establishing communication between said first compartment and said one tube member, a second disc-shaped baffle plate fitted into said barrel and being disposed at right angles to the axis of said barrel, said second bafile plate being spaced from the other of said closure plates thereby forming a second compartment therewith, said second baflle plate having an opening which receives in sealing relation the distal end of the end portion of the other tube member thereby establishing communication between said second compartment and said other tube member, both said tube members having a plurality of longitudinally spaced apertures therein arranged in a straight line located in said plane of said axes adjacent to the periphery of said barrel, said apertures extending from one end to the other of each tube member, a plurality of deflector tabs on said tube members adjacent to said apertures, respectively, and extending inwardly of said tube members, there being one tab for each aperture, said tabs being secured to said tube members and angling inwardly in a direction extending from said first barrel end toward the second barrel end, and a third disc-shaped bafile plate fitted into said barrel and being disposed at right angles to the axis of said barrel, said third bafile plate being spaced from and disposed between said first and second baffie plates thereby defining additional compartments, said third baffle plate having two diametrically spaced openings which receive, respectively, said two tube members, said third bafile plate being secured to said two tube members, and a clearance opening provided in said (third baffle plate in the central portion thereof adjacent to said two tube members for providing direct communication between said additional compartments.

4. A multi-pass engine m-utfler comprising a barrel having intake and exhaust chambers at the opposite ends thereof, respectively, partition means providing a pinrality of intenmediate chambers tandemly arranged between said intake and exhaust chambers, said partition means having apertures therein thereby providing communication between adjacent ones of said intermediate chambers, a first elongated conduit interconnecting said intake and one of said intermediate chambers, a second of said intermediate chambers being between said intake and said one intermediate chamber, a second elongated conduit interconnecting said exhaust chamber and another of said intermediate chambers, both said intake and exhaust conduits having orifices in the walls thereof, said orifices interconnecting said conduits and said intermediate chambers, said intake and exhaust chambers bebarrel in the process of mufiling exhaust gases.

5. A three pass .englne mutiler comprising an elongated barrel, first and second conduits having axes and being disposed Within said barrel, said axes of said conduits being parallel and lying in'a single plane which also includes the cross-sectional diameters of said barrel,

said conduits being securedin longitudinally offset relation whereby one distal end portion of each conduit ex tends beyond the adjacent end of the other conduit, two closure plates on opposite ends, respectively, of said barrel, entrance and exhaust ducts secured to said two closure plates, respectively, communicating with the interior oat said barrel, a first bafile plate being spaced from one of said closure plates, thereby forming a first compartment therewith, said first bafile plate having a first opening therein, said first opening receiving in sealing relation said distal end portion of one of said conduits, said first bafile plate being in sealing relation with said barrel, a second baffle plate being spaced from the other oi said closure plates thereby forming a second compartm'ent therewith, said second bafiie plate having a second opening therein, said second opening receiving in sealing relation said distal end portion of the .other of said conduits, said second baflie plate being in sealing relation with said barrel, both said conduit members having a plurality of longitudinally spaced apertures therein arranged in a straight line, said straight line being located in said plane of said conduit axes with both of said axes lying in said plane between said line oi said first conduit and said line of said second conduit, said apertures extending from one end to the other end of each conduit and being adjacent the periphery of said barrel, a plurality of deflector tabs on said conduit members adjacent to said apertures, respectively, and extending inwardly of said conduit members and angling in a direction extending from said entrance duct toward said exhaust duct, there being one tab for each aperture, and at least one third bafile plate intermediate and spaced irom said first and second baffle plates thereby forming additional compartments, said third baffie plate having a third opening therein, said first and second conduits passing through said third opening, said third baflle plate being secured to said barrel and said conduits.

6. A three-pass engine mufiler comprising an elongated barrel, first and second conduits having axes and being disposed within said barrel, the axes of said conduits being parallel and lying in a single plane which also includes the cross sectional diameters of said barrel, said conduits being secured in longitudinally offset relation whereby one distal end portion of each conduit extends (beyond the adjacent end of the other conduit, two closure plates on opposite ends, respectively, of said barrel, entrance and exhaust ducts secured to said two closure plates, respectively, communicating with the interior of said barrel, a first bafile'plate being spaced from one of said closure plates thereby forming a first compartment therewith, said first bafile plate having a first opening therein, said first opening receiving in sealing relation said distal end p-ortion'ot one of said conduits,'said first bame plate'being in sealing relation with said barrel, ,a second'baffie plate being spaced from the other of said closure plates thereby'form ing a second compartment J therewith, said second baffie plate having a second openingtherein, said second opening receiving in sealing relation said distal end portion of the other of said conduits,

said second baffle plate being in sealing relation with said barrel, both said conduit members having a plurality of longitudinally spaced apertures therein arranged in a straight line, said straight line being located in said plane of said conduit'axes with both of said axes lying in said plane between said line of said first conduit and said line of said second conduit, said apertures extending from one end to the other end of each conduit and being adjacent the periphery of said barrel, a plurality of deflector tabs on said conduit members adjacent to said apertures, respectively, and extending inwardly of said conduit memhers and angling in a direction extending from. said entrance duict toward said exhaust du ct, there being one tab for each aperture, and a third baffle plate secu red in said barrel between said first and second bafile plates j in spaced relation thereto thereby defining additional compartments, said third baffle plate having two diametrically spaced openings which reecivesaid two conduits, respectively, said third bafile plate being sealingly secured to said two conduits and said barrel and having an orifice therein, said orifice providing communication between said additional compartments, said orifices interconnecting said additional chambers.

References Cited by the Examiner UNITED STATES PATENTS LEO SMILOW, Primary Examiner. 

5. A THREE-PASS ENGINE MUFFLER COMPRISING AN ELONGATED BARREL, FIRST AND SECOND CONDUITS HAVING AXES AND BEING DISPOSED WITHIN SAID BARREL, SAID AXES OF SAID CONDUITS BEING PARALLEL AND LYING IN A SINGLE PLANE WHICH ALSO INCLUDES THE CROSS-SECTIONAL DIAMETERS OF SAID BARREL, SAID CONDUITS BEING SECURED IN LONGITUDINALLY OFFSET RELATION WHEREBY ONE DISTAL END PORTION OF EACH CONDUIT EXTENDS BEYOND THE ADJACENT END OF THE OTHER CONDUIT, TWO CLOSURE PLATES ON OPPOSITE ENDS, RESPECTIVELY, OF SAID BARREL, ENTRANCE AND EXHAUST DUCTS SECURED TO SAID TWO CLOSURE PLATES, RESPECTIVELY, COMMUNICATING WITH THE INTERIOR OF SAID BARREL, A FIRST BAFFLE PLATE BEING SPACE FROM ONE OF SAID CLOSURE PLATES, THEREBY FORMING A FIRST COMPARTMENT THEREWITH, SAID FIRST BAFFLE PLATE HAVING A FIRST OPENING THEREIN, SAID FIRST OPENING RECEIVING IN SEALING RELATION SAID DISTAL END PORTION OF ONE OF SAID CONDUITS, SAID FIRST BAFFLE PLATE BEING IN SEALING RELATION WITH SAID BARREL, A SECOND BAFFLE PLATE BEING SPACED FROM THE OTHER OF SAID CLOSURE PLATES THEREBY FORMING A SECOND COMPARTMENT THEREWITH, SAID SECOND BAFFLE PLATE HAVING A SECOND OPENING THEREIN, SAID SECOND OPENING RECEIVING IN SEALING RELATION SAID DISTAL END PORTION OF THE OTHER OF SAID CONDUITS, SAID SECOND BAFFLE PLATE BEING IN SEALING RELATION WITH SAID BARREL, BOTH SAID CONDUIT MEMBERS HAVING A PLURALITY OF LONGITUDINALLY SPACED APERTURES THEREIN ARRANGED IN A STRAIGHT LINE, SAID STRAIGHT LINE BEING LOCATED IN SAID PLANE OF SAID CONDUIT AXES WITH BOTH OF SAID AXES LYING IN SAID PLANE BETWEEN SAID LINE OF SAID FIRST CONDUIT AND SAID LINE OF SAID SECOND CONDUIT, SAID APERTURES EXTENDING FROM ONE END TO THE OTHER END OF EACH CONDUIT AND BEING ADJACENT THE PERIPHERY OF SAID BARREL, A PLURALITY OF DEFLECTOR TABS ON SAID CONDUIT MEMBERS ADJACENT TO SAID APERTURES, RESPECTIVELY, AND EXTENDING INWARDLY OF SAID CONDUIT MEMBERS AND ANGLING IN A DIRECTION EXTENDING FROM SAID ENTRANCE DUCT TOWARD SAID EXHAUST DUCT, THERE BEING ON TAB FOR EACH APERTURE, AND AT LEAST ONE THIRD BAFFLE PLATE INTERMEDIATE AND SPACED FROM SAID FIRST AND SECOND BAFFLE PLATES THEREBY FORMING ADDITIONAL COMPARTMENTS, SAID THIRD BAFFLE PLATE HAVING A THIRD OPENING THEREIN, SAID FIRST AND SECOND CONDUITS PASSING THROUGH SAID THIRD OPENING, SAID THIRD BAFFLE PLATE BEING SECURED TO SAID BARREL AND SAID CONDUITS. 